Gutta-percha insulation material



Patented Nov. 14, 1933 1,935,321. GUTTA4PERCHA INSULATION MATERIAL Archie R.- Kemp, Westwood, and John H. Ingmanson, Bloomfield, N. J., assignors to 'Bell Telephone Laboratories, Incorporated, New York, N-. Y;, a corporation of New York No Drawing. Application February 3, 1930 Serial No. 425,710

' 8 Claims.

This invention relates'to gutta-percha insulation materials and to methods of producingsuch materials, andmore particularly to improvements in materials of this kind for use in long deep sea cables especially designed for higher frequencies 'than the usual cable telegraph signaling freimproved gutta-percha as a compounding material for deep sea cable insulation material which has electrical properties as good as or better than practically pure gutta-hydrocarbon.

"Another object of the invention is to provide an improved gutta-percha of this kind WhiChfbfisides having satisfactory electrical properties has improved mechanical properties.

Still another object is to provide a method of .treating gutta-percha whereby inferior grades may be brought up to standard requirements as to mechanical properties as well as to electrical characteristics; or whereby such inferior gutta-.

percha may be improved to have, besides the required mechanical properties better electrical characteristics than those usually required for even high speed telegraph submarine cables. Still another object is to provide a method of producing such a material which is commercially feasible. I v 11 x For the purpose of the present specification and the claims appended theret the term guttapercha includes the various grades of balata. v

In accordance with the invention guttaepercha is treated in such a manner that it is deprived ofcertain of its resinous constituents which have been found to have unsatisfactory electrical properties under certain sea bottom conditions, and other resins, naturally present in the gutta-. percha or else obtained from other sources and which have been found .to have satisfactory electrical properties, are utilizedin the gutta-percha product to addthermo-plastic characteristics thereto, and possibly to afford a protective action, as well as to improve its electrical characteristics.

The mechanical properties jwhich in present day practice are required of the compound comprising the main insulatingvbody in deep sea cables include thermo-p'lasticity, ability to be extruded in a uniform fashionaround the conductor at the usual extrusion temperatures, limited cold flow at room and sea bottom temperatures, toughness and flexibility at room temperatures, etc. The mechanical properties of the component substances of the insulating compoundmay, of course, differ somewhat from these standards, inasmuch as these substances "usually are chosen with regard to their ability "to complement each other in this respect. 7

An important electrical characteristic of the insulating material is the le'akance factor G/C,

which is the ratio of leakance to capacity of a sample. This factor is of greater importance as the frequency of g the applied current increases and itshould be keptiflow under sea bottom conditions to insure a low attenuation of signals over a long cable. s

It has before been known that gutta-percha, and therefore also balata, can be improved electrically by the removal of resins therefrom. It

has therefore been concluded that the resins th'emselveshaveless satisfactory electrical properties than has the guttaehydrocarbon.

The resins of gutta-perchaincluding those of balata, have before been separated and certain of their physical and chemical characteristics have been determined. They have been found soluble in hot alcohola nd in petroleum naphtha,

but is: nearly insoluble in cold alcohol. The fiuavil fraction is a yellow product melting at low temperatures and soluble in cold alcohol as well as=in petroleum naphtha.

In an investigation conducted in an attempt to determine how gutta-percha, and particularly balata, may be improved for the purpose of deep sea cable insulation, we have found that the less satisfactory electrical properties may be ascribed particularly to the resins included inthe fluavil' group or to some constituent contained in or intimately associated with the fluavil, whereas those of the albane group have been found to have more satisfactory electrical characteristics.

We have furthermore found that the fiuavil may be separated from the albane as well as from the gutta-hydrocarbon of a body of guttapercha by solution, for example, in certain a1- cohols of the aliphatic series at ordinary room temperatures.

In carrying out the invention it is possible to proceed by different methods of removing the fluavil from the gutta-percha.

In accordance with one method, the whole resins are practically completely separated from the gutta-hydrocarbon by extraction; the fiuavil is then extracted from the whole resin, and the albane residue restored to the gutta-hydrocarbon.

In accordance with another method, only the fluavil is removed by extraction, the albane remaining in the gutta-percha.

Another method may constitute a combination of these two methods.

In accordance with still other methods albanes may be taken from other bodies of gutta-percha to replace the total resin content of the body of gutta-percha which is to be improved, or to replace more or less of such portions of the resin content which has already been or is subsequently to be removed from the body of gutta-percha Foreign albanes derived from other resinous materials'such as chicle, may furthermore be incorporated in the gutta-percha for the present purpose. 1

Sample A.In a specific instance, a quantity of balata of average quality was thoroughly Washed in warm water for removal of dirt, dried in themasticator and formed into a sheet about one half millimeter in thickness. The resultant product was found to have the following a Per cent by Weight Moisture content; .92 Resinous content 51.5

Electrical tests at 0 C. gave the following results:

Applied Leakance Dielectric frequency factor constant I G/C K 1000 0/5 107 3. 13 2000 c/s 241 3. 11 3000 0/5 398 3. 00 10000 o/s 1815 3.03

Sample B.A piece of Sample A, 400 grams in 7 Per cent by weight Moisture content .14 Resinous content 37.9

Electrical tests at 0 0. gave the following data:

1000 c/s 7. 5 2. 71 v 2000 0/5 30 2. 71 30000 5 03 2. 10000 0/5 445 l 2. 70

Sample C.-Another piece of Sample A, 400 grams in weight, was subjected to a single extraction for 24 hours at 24 C. in 4000 cm of methanol. It was then washed for the removal of the solvent and dried in the masticator after which it was found to have the following Per cent by weight Moisture content .75 Resinous content 36.?

Electrical tests at 0 C. gas the following data:

I G/G K Sample D.Another piece of Sample A, 300 grams in weight was subjected to a single extraction for 24 hours at 24 C. in 1800 cm of ethanol. It was then washed for the removal of the solvent and dried in the masticator after which it was found to have the following Sample E.Another piece of Sample A, 300 grams in weight, was subjected to a single extraction for 24 hours at 24 C. in 3000 cm of ethanol. It was then Washed for the removal of the solvent and dried in themasticator after Which itwas found to have the following Per cent by weight Moisture content 1.03 Resinouscontent ..'...1 30.5

Electrical tests at 0 C. gave the following data:

r o/o K 1000 c/s 5. 3 2.89 2000 c/s 18.7 2. 89 3000 0/5 32 2.89

The Samples B to E are examples of partial extraction of the resins at low temperatures whereby mainly the fluavil is removed. The electrical data show that both the leakance factor CT/C and the dielectric constant K have been greatly improved by the relatively limited extraction. The different products were found to have mechanical properties which make them suitable for submarine cable insulation both in regard to manufacturing and laying requirements and as to operating requirements. As-a matter of fact the mechanical properties of these samples were'greatly improved over those of the original balata of Sample A.

Sample F.A piece of Sample A'was subjected to two successive extractions each of 24 hours in petroleum naphtha at 10 C; the gasolinewas carefully removed and the productwas washed in hot water and dried in the masticator and was found to have the following s p i methyl ethyl ketonaas well as'mixturesofsome Moisture content j of these. By the proper choice of the three lac-s Rsssssss ssnssss:::::':i::::::::::::::l 411- tors m n d is s p ssi l so .sssssss 5 Electrical tests at 0C. gave the following data:

f G/C K Sample G.A whole resin extracted from balata was subjected to, electrical tests at 0 C. and gave the following data:

1000 0/5 53. 0 3. 20 2000 c/s 180.5 3. 25 3000 c/s 367 3. 24

Sample H .75 grams of a whole balata resin was subjected to an extraction for 6 hours at room temperature in 900 cm of ethanol after which it was filtered and the residue washed in ethanol and the alcohol carefully removed.

Electrical tests at 0 C. gave the following data:

1000 0/5 11.6 2. 2 2000 c/s 21. 3 2. 2 3000 0/5 to 2. 2

-- of the deresinated balata of Sample F with mechanical properties satisfactory for deep sea cable insulation.

Though the various samples described had all been'taken from balata, similar treatments may be given to any other type of gutta-percha with corresponding results. It is furthermore pos- V sible to extract and separate the albanes from 's'mrieties of guttarpercha. Again, other natural 0 any one or more gutta-peroha varieties and use them in the desired proportions as plasticizing agents for any one variety or combination of albanes or albane rich substances may be incorporated by Well known mixing processes as a plasticizing agent in any of these instances, such as chicle or the albanes of chicle.

It is obvious that the temperatures at which the fluavil extraction from gutta-percha is made may be somewhat different from room temperatures depending upon the solvent used, the time allowed for the extraction and upon the degree of extraction desired. Thus a very quick extraction may be made with methanol at temperatures as high as 60-65 0. Besides the preferred solvents. methanol and ethanol, a number of other solvents may be used such as propyl alcohol, acetone,

more or less ofthe fiuavil constituent and also certain of the albanes from the albane con/Stitu-s entlof the gutta-spercha.

Various methods describedsas examples ofthis invention have involved the removal of fluavil from the gutta-percha. It is possible that the poor electrical properties of fluavil are not inherent to the main bulk of the fiuavil but are due to smaller quantities of substances which are more closely associated with the fluavil than with the albane and which may be less easily separated therefrom, Thus the fiuavil extractions have been found to contain small quantities of free acids and still smaller quantities of free alcohol. These quantities appear, however, to be sufficient to justify the assumption that one or both of these substances are the cause of the degradation in the electrical properties of guttapercha.

It should be understood that the mechanical properties of any particular body of guttapercha which is suitable for incorporation in a cable insulating material are not necessarily identical with the mechanical properties required for such insulating material. By the methods forming part of this invention any quality of gutta-percha, which in present practice is considered suitable for use in admixture with other qualities of gutta-percha or with other compounding materials may have its electrical properties improved and at the same time may retain its mechanical properties somewhat improved.

It is Within the scope of this invention toadmix with the above described gutta-hydrocarbon and albane composition such materials as: natural rubber of all sorts treated or untreated to remove objectionable constituents, such as soluble salts and proteins; synthetic rubber prepared by polymerizing any of the known conjugated dienes; waxes which are derived from natural sources or prepared synthetically; antioxidants such as phenyl alpha napthylamine or phenylbeta-napthylamine or any other product which may act to modify the properties of the gutta-hydrocarbon and albane composition in the direction to attain the desired product.

What is claimed is:

1. A gutta-percha product comprising resin poor gutta-percha in which albane has been incorporated as a plasticizing agent.

2. A gutta-percha product comprising a greatly deresinatedgutta-percha and as a plasticizing agent a foreign albane, such as chicle albane.

3. A gutta-percha product in which resins hav-' ing better electrical properties have replaced natural resin constituents having poorer electrical properties. 0

4. A method of, improving the electrical properties of gutta-percha which comprises extracting at least a portion of the resins therefrom, sep arating from the extracted resins at least a portion of those constituents which have the poorer electrical properties and restoring a portion of the remaining constituents to the gutta-percha.

5. A method of treating gutta-percha which comprises extracting a portion of the resins therefrom, separating the albanes from the extract and incorporating said separated albanes in the gutta-percha from which resin was removed.

6. A method of improving the mechanical properties of at least partially deresin'ated guttaor even have these its erties of gutta-percha which has been considerably deresinated which comprises mixinga foreign substance therewith, the main natural constitwent of which is albarnei 1,935,32r v p 8. A method of improving the electrical and mechanical properties of gutted-hydrocarbon by mixing therewith an albane rich substance such as chicle,

' ARCHIE R. KEMP.

JOHN H. INGMANSON. 

